U.S. Pat. Nos. 4,351,077 to Hofmann and 4,642,833 to Stoltz, et al., incorporated herein in their entireties by this reference, disclose automatic, water-interruption-type suction swimming pool cleaners having flexible annular discs. These discs are typically mounted near the inlets of the suction cleaners and designed to contact pool surfaces when in use. By doing so, the discs decrease the tendency of the cleaners to disengage from pool surfaces, particularly when the cleaners are negotiating transition regions between walls and floors.
U.S. patent application Ser. No. 08/103,930 ("the parent-in-part application"), also incorporated herein in its entirety by this reference, describes other exemplary swimming pool cleaner discs (and associated equipment). These discs incorporate upwardly-extending, non-truncated fins protruding radially from their peripheries. The serpentine peripheries themselves, moreover, define a plurality of tongues, providing increased flexibility over even existing scalloped discs. Concurrently, the fins supply sufficient rigidity to the discs disclosed in the parent-in-part application to enable them to ride over various objects, including many drains, lights, valves, and nozzles, projecting from internal surfaces of pools.
Additional features of the discs illustrated in the parent-in-part application include curved radii between the fins and the lower surfaces of the discs, providing smooth transitions therebetween. The underside of each disc also contains an integrally-formed ramped segment surrounding the (nominally circular) central aperture of the disc. This ramp assists the pool cleaner in negotiating obstacles, supplying a smooth progression from the disc bottom to the bottom of the cleaner footpad (which the disc surrounds in use), which too may include a ramp. Multiple openings through the discs of the parent-in-part application enable fluid to pass from one surface of each disc to the other, maintaining a boundary fluid layer between the lower surface of the disc and the adjacent surface of the pool. These openings facilitate movement of the disc relative to the pool cleaner and allow dirt and debris to be entrained in the flow of fluid through the openings and in the boundary layer.